This application is based on Patent Application No. 2000-366291 filed Nov. 30, 2000 in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an ink-jet printing method and an ink-jet printing apparatus and specifically to a configuration for reducing bleeding at a boundary between black and color image areas printed when black ink and other kinds of color ink are used for printing.
2. Description of the Related Art
A printing apparatus having a function of a printer, a copy machine, a facsimile or the like, or a printing apparatus used as an output device of information processed in a composite electronic device including a computer and a word processor, a work station and so on, is structured so that images (including characters and so on) are printed on a printing medium such as a printing sheet and a plastic thin plate based on image information (including character information). Such a printing apparatus is, by a printing method, classified into an ink-jet system, a wire dot system, a thermal transfer system, a laser beam system and the like. Among them, a printing apparatus using the ink-jet system (hereinafter, referred to as an ink-jet printing apparatus) performs printing by ejecting ink to a printing medium from a printing head, and has many advantages such that high resolution printing can be achieved more easily than other printing systems, high-speed and high quiet printing can be performed, and a device is available at relatively low cost.
Such ink-jet printing apparatus on the other hand has been much requested to be able to perform color printing, and a number of color ink-jet printing apparatuses have been provided. In general, in order to improve a printing speed and so on, as a printing head having a plurality of printing elements arranged integrally, the ink jet printing apparatus uses a printing head, in which a plurality of ink ejection openings and ink paths, that compose ink ejection portions, are integrated, and further includes a plurality of printing heads for respective colors of ink to be adapted to color printing.
FIG. 1 is a perspective view mainly showing an example of a schematic configuration of a printing section in an ink-jet printing apparatus.
In FIG. 1, printing heads 102 and ink cartridges 101 are detachably mounted on a carriage 106 and are used for printing. More specifically, the printing heads and the ink cartridges are used correspondingly to color inks of black (Bk), cyan (C), magenta (M), and yellow (Y), respectively and the printing heads for the respective inks are scanned for printing by the move of the carriage 106. Hereinafter, the above mentioned scanning is referred to as main scanning and its direction is referred to as a main scanning direction. The carriage 106 is engaged to a guide shaft 107 so as to slide thereon. The carriage 106 can be moved thus along the guide shaft 107 by driving of a driving mechanism such as a motor and a belt (not shown).
FIG. 2 shows ejection openings disposed on each of the printing heads 102, taken along direction xe2x80x9czxe2x80x9d (FIG. 1). In FIG. 2, reference numeral 201 denotes n ejection openings arranged on the printing head 102, and the ejection openings are arranged at a density of N dpi. A variety of ejection systems may be adopted for such a printing head. For example, a method may be applicable in which a bubble is produced in ink by using thermal energy generated by an electro-thermal converter and ink is ejected by pressure of the bubble.
Referring to FIG. 1 again, reference numeral 103 denotes a paper feeding roller, which rotates in a direction shown by an arrow in FIG. 1 while pressing a printing sheet P in cooperation with an auxiliary roller 104 to on necessary move the printing sheet P as a printing medium in y direction (hereinafter, referred to as a xe2x80x9csub-scanning directionxe2x80x9d). Further, reference numeral 105 denotes a paper feeding roller, which feeds printing sheets and also functions as applying constant tension to the printing sheet P similarly to the rollers 103 and 104.
During a non-printing operation, the carriage 106 is shifted to a home position h and waits for a printing command. During a printing operation, the carriage 106 moves in x direction to scan the printing heads 102 of respective inks. During this scanning operation, ejecting ink from the respective n ejection openings 201 in accordance with image information can perform printing. When the above main scanning completes printing of image information on the end of a printing sheet P, the carriage returns to a printing start position while the printing sheet P is moved at a predetermined amount. Thereafter, scanning and printing in x direction are repeated.
When an image and the like are printed, a variety of image-quality elements are demanded including coloring, gradation, and a uniform density of a printed image. Particularly, it has been known that regarding the uniform density, due to slight unevenness of ejection openings on manufacturing that occurs in a process of manufacturing a printing head, an amount of ejected ink and an ejecting direction may vary among the ejection openings, resulting in uneven density of the printed image.
A specific example of such occurrence of uneven density will be explained referring to FIGS. 3A to 3C and 4A to 4C. In FIG. 3A, reference numeral 31 denotes a printing head, which is composed of eight ejection openings 32. Reference numeral 33 denotes ink drops (ink droplets) ejected from the eight ejection openings 32. Ink is ideally ejected with substantially an equal amount and substantially in the same direction as shown in FIG. 3A. Such ideal ejection would form ink dots substantially equal in size on a printing sheet as shown in FIG. 3B, and entirely obtain a uniform image without variation in density (FIG. 3C).
However, as described above, ejection openings actually have unevenness to some extent. In this case, when printing is performed in the above manner, as shown in FIG. 4A, ink drops ejected from the ejection openings vary in size and direction, resulting in ink dots of FIG. 4B that are varied in size and printing position on a printing sheet.
Consequently, for example, a part on a printing sheet, which do not satisfy 100% of an area factor and come out as a ground of the printing sheet, appears periodically in a direction of aligning the ejection openings, resulting in white bands. Or conversely, an image including a part, in which dots formed overlap each other more than necessary, resulting in a black band, is printed. In other words, such an image has a density distribution shown in FIG. 4C in a direction of aligning the ejection openings. The density distribution is visually recognized as an uneven density. Moreover, bands may appear due to variations in an amount of feeding printing sheets.
As a solution for such uneven density, for example, Japanese Patent Laid-Open No. 06-143618 discloses the following method. Referring to FIGS. 4A to 4C and FIGS. 5A to 5C, the method will be explained briefly.
As shown in FIG. 5A, this method completes printing for the same printing area as that shown in FIG. 4B by three times of scanning of the printing head 31, between which the printing sheet is moved at an amount corresponding to four pitches of ejection openings. More specifically, a scanning area, which is equivalent to a half of the above mentioned printing area and corresponds to four ejection openings, is completed by two times of scanning. At this moment, for the scanning area, in the first scanning lower four of the eight ejection openings of the printing head is used. In the second scanning after feeding at an amount corresponding to four ejection openings, upper four ejection openings are used for printing. And, in the first scanning for each of the ejection openings, printing is performed on image data which is thinned out to about a half according to a predetermined thinning pattern. In the second scanning, printing is performed on the remaining half of the image data so as to complete printing. Hereinafter, such a printing method is referred to as a multi-pass printing method.
According to the multi-pass printing method, even in the case of using a printing head including ejection openings having unevenness in ejecting characteristics as shown in FIGS. 4A to 4C, variations in dot size and printing position due to this unevenness is dispersed. Then, as shown in FIG. 5B, a printed image has no irregularity of dot formation as recognized as the black band or the white band and is recognized as a substantially even distribution of density shown in FIG. 5C.
When such multi-pass printing is carried out, thinning is performed based on thinning patterns, which are complementary to each other, in the first scanning and the second scanning. As pixel patterns for this thinning pattern, as shown in FIGS. 6A to 6C, checkered patterns are generally used for pixels in rows and columns. In this case, in the first scanning, pixels corresponding to black parts as shown in FIG. 6A of the checkered pattern are printed, and in the second scanning, pixels corresponding to white parts as shown in FIG. 6B are printed, then printing is entirely completed (FIG. 6C).
As described above, for each line composed of dots arranged in the scanning direction, two different ejection openings are used so that printing of image performed. Hence, it is possible to obtain a high-quality image with reduced unevenness in density.
In addition to the above technique for reducing variations in density, as another factor for improving the picture quality of a printed image, a technique for preventing bleeding at a boundary between a black image and a color image has been known. For example, Japanese Patent Laid-Open No. 06-135014 discloses a method for using a predetermined ejection portion of an ejection opening group for ejecting black ink when a black image printed with black ink and a color image printed with color ink are adjacent to each other. Hence, scanning for printing a black image is separated from scanning for printing a color image, and the scanning is not performed sequentially. More specifically, since another scanning is executed between the scanning for printing a black image and the scanning for printing a color image, which is adjacent to the black image, it is possible to provide time for fixing a previously printed image such as the black image, thereby achieving high-quality printing for reducing the bleeding at the boundary between the black image and the color image.
However, in the case of using the multi-pass printing mentioned before, when it is intended that the bleed at a boundary (hereinafter, also referred to as xe2x80x9cbleeding in colorsxe2x80x9d) is reduced between the black image and the color image, the method of Japanese Patent Laid-Open No. 06-135014 cannot be used as it is. More specifically, in the method disclosed in the above publication, the black image and the color image are printed by a single scanning of a printing head (hereinafter, referred to as xe2x80x9cone-pass printingxe2x80x9d). Hence, the method is different in precondition from the case using the multi-pass printing, by which printing on a predetermined area is completed by a plurality of times of scanning. Therefore, even when the method is used as it is, scanning for obtaining fixing time cannot be provided.
Further, in addition to the bleeding in colors, the one-pass printing and the multi-pass printing are different from each other regarding a phenomenon in which a printed part appears whitish by interference of inks when inks of a plurality of colors land on a printing medium. Such a difference in the phenomenon appears because the multi-pass printing is different from the one-pass printing in permeation and fixing conditions of ink to the printing medium due to fewer dots printed in a unit area for unit time in the multi-pass printing, as well as because the multi-pass printing has the effect of preventing print density from becoming uneven.
The object of the present invention is to provide an ink-jet printing method and an ink-jet printing apparatus for printing a high-quality image with reduced bleeding in colors that may appear in multi-pass printing.
In a first aspect of the present invention, there is provided an ink jet printing method of performing printing by ejecting ink to a printing medium from a printing head while scanning the printing head relatively to the printing medium,
wherein the printing head is provided, for at least two kinds of ink, with ejection opening rows each including a plurality of ejection openings arranged in a direction different from a direction of the scanning,
printing is performed in which the number of times of scanning is m (m is positive integer), which is required for completing an image by means of a first ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, and the number of times of scanning is n (n is positive integer), which is required for completing an image by means of a second ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, where at least one of m and n is 2 or more, and an amount at which the printing medium is moved for each time of the scanning in a direction different form the direction of the scanning is L (L is positive integer),
and the second ejection opening row is parted from the first ejection opening row toward a discharge side regarding moving of the printing medium at a distance (m+a)xc3x97L (a is positive integer),which is measured as a distance between respective ejection openings located at a feed side ends regarding the moving of the printing medium.
In a second aspect of the present invention, there is provided an ink jet printing method of performing printing by ejecting ink to a printing medium from a printing head while scanning the printing head relatively to the printing medium,
wherein the printing head is provided, for at least two kinds of ink, with ejection opening rows each including a plurality of ejection openings arranged in a direction different from a direction of the scanning,
printing is performed in which the number of times of scanning is m (m is positive integer), which is required for completing an image by means of a first ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, and the number of times of scanning is n (n is positive integer), which is required for completing an image by means of a second ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, where at least one of m and n is 2 or more, and an amount at which the printing medium is moved for each time of the scanning in a direction different form the direction of the scanning is L (L is positive integer),
and the second ejection opening row is parted from the first ejection opening row toward a feed side regarding moving of the printing medium at a distance (m+a)xc3x97L (a is positive integer),which is measured as a distance between respective ejection openings located at a discharge side ends regarding the moving of the printing medium.
In a third aspect of the present invention, there is provided an ink jet printing method of performing printing by ejecting ink to a printing medium from a printing head while scanning the printing head relatively to the printing medium,
wherein the printing head is provided, for at least two kinds of ink, with ejection opening rows each including a plurality of ejection openings arranged in a direction different from a direction of the scanning,
printing is performed in which the number of times of scanning is m (m is positive integer), which is required for completing an image by means of a first ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, and the number of times of scanning is n (n is positive integer), which is required for completing an image by means of a second ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, where at least one of m and n is 2 or more, and an amount at which the printing medium is moved for each time of the scanning in a direction different form the direction of the scanning is L (L is positive integer),
and the second ejection opening row is parted from the first ejection opening row toward a discharge side regarding moving of the printing medium at a distance which is larger than (m+a)xc3x97L (a is positive integer) and is shorter than (m+a+1)xc3x97L, the distance being measured as a distance between respective ejection openings located at a feed side ends regarding the moving of the printing medium.
In a forth aspect of the present invention, there is provided an ink jet printing method of performing printing by ejecting ink to a printing medium from a printing head while scanning the printing head relatively to the printing medium,
wherein the printing head is provided, for at least two kinds of ink, with ejection opening rows each including a plurality of ejection openings arranged in a direction different from a direction of the scanning,
printing is performed in which the number of times of scanning is m (m is positive integer), which is required for completing an image by means of a first ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, and the number of times of scanning is n (n is positive integer), which is required for completing an image by means of a second ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, where at least one of m and n is 2 or more, and an amount at which the printing medium is moved for each time of the scanning in a direction different form the direction of the scanning is L (L is positive integer),
and the second ejection opening row is parted from the first ejection opening row toward a feed side regarding moving of the printing medium at a distance which is larger than (m+a)xc3x97L (a is positive integer) and is shorter than (m+a+1)xc3x97L, the distance being measured as a distance between respective ejection openings located at a discharge side ends regarding the moving of the printing medium.
In a fifth aspect of the present invention, there is provided an ink jet printing method of performing printing by using a printing head having a first ejection opening row including a plurality of ejection openings ejecting a first kind of ink and a second ejection opening row including a plurality of ejection openings ejecting a second kind of ink different from the first kind of ink and by ejecting ink to a printing medium from the printing head, the method comprising the step:
controlling the printing for an area, which has a length corresponding to a divided length of an ejection opening arranged length of at least one of the first and second ejection opening rows, to be completed by scanning the at least one of the first and second ejection opening rows to the area a plurality of times, between successive two times of scanning the printing medium is moved at a distance of the divided length, and assigning different ejection opening to the area from each of the plurality of times of scanning,
wherein printing of a first image is completed by using the first kind of ink ejected by the first ejection row, then printing of a second image adjacent to the first image completed is completed by using the second kind of ink ejected by the second ejection row, and the time of scanning in which printing is not performed on the area of the first image exists between the time of a last scanning for completing the first image and the time of a first scanning for printing the second image.
In a sixth aspect of the present invention, there is provided an ink jet printing apparatus for performing printing by ejecting ink to a printing medium from a printing head while scanning the printing head relatively to the printing medium,
wherein the printing head is provided, for at least two kinds of ink, with ejection opening rows each including a plurality of ejection openings arranged in a direction different from a direction of the scanning,
printing is performed in which the number of times of scanning is m (m is positive integer), which is required for completing an image by means of a first ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, and the number of times of scanning is n (n is positive integer), which is required for completing an image by means of a second ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, where at least one of m and n is 2 or more, and an amount at which the printing medium is moved for each time of the scanning in a direction different form the direction of the scanning is L (L is positive integer),
and the second ejection opening row is parted from the first ejection opening row toward a discharge side regarding moving of the printing medium at a distance (m+a)xc3x97L (a is positive integer),which is measured as a distance between respective ejection openings located at a feed side ends regarding the moving of the printing medium.
In a seventh aspect of the present invention, there is provided an ink jet printing apparatus for performing printing by ejecting ink to a printing medium from a printing head while scanning the printing head relatively to the printing medium,
wherein the printing head is provided, for at least two kinds of ink, with ejection opening rows each including a plurality of ejection openings arranged in a direction different from a direction of the scanning,
printing is performed in which the number of times of scanning is m (m is positive integer), which is required for completing an image by means of a first ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, and the number of times of scanning is n (n is positive integer), which is required for completing an image by means of a second ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, where at least one of m and n is 2 or more, and an amount at which the printing medium is moved for each time of the scanning in a direction different form the direction of the scanning is L (L is positive integer),
and the second ejection opening row is parted from the first ejection opening row toward a feed side regarding moving of the printing medium at a distance (m+a)xc3x97L (a is positive integer),which is measured as a distance between respective ejection openings located at a discharge side ends regarding the moving of the printing medium.
In an eighth aspect of the present invention, there is provided an ink jet printing apparatus for performing printing by ejecting ink to a printing medium from a printing head while scanning the printing head relatively to the printing medium,
wherein the printing head is provided, for at least two kinds of ink, with ejection opening rows each including a plurality of ejection openings arranged in a direction different from a direction of the scanning,
printing is performed in which the number of times of scanning is m (m is positive integer), which is required for completing an image by means of a first ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, and the number of times of scanning is n (n is positive integer), which is required for completing an image by means of a second ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, where at least one of m and n is 2 or more, and an amount at which the printing medium is moved for each time of the scanning in a direction different form the direction of the scanning is L (L is positive integer),
and the second ejection opening row is parted from the first ejection opening row toward a discharge side regarding moving of the printing medium at a distance which is larger than (m+a)xc3x97L (a is positive integer) and is shorter than (m+a+1)xc3x97L, the distance being measured as a distance between respective ejection openings located at a feed side ends regarding the moving of the printing medium.
In a ninth aspect of the present invention, there is provided an ink jet printing apparatus for performing printing by ejecting ink to a printing medium from a printing head while scanning the printing head relatively to the printing medium,
wherein the printing head is provided, for at least two kinds of ink, with ejection opening rows each including a plurality of ejection openings arranged in a direction different from a direction of the scanning,
printing is performed in which the number of times of scanning is m (m is positive integer), which is required for completing an image by means of a first ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, and the number of times of scanning is n (n is positive integer), which is required for completing an image by means of a second ejection opening row set for use out of the ejection opening rows for the at least two kinds of ink, where at least one of m and n is 2 or more, and an amount at which the printing medium is moved for each time of the scanning in a direction different form the direction of the scanning is L (L is positive integer),
and the second ejection opening row is parted from the first ejection opening row toward a feed side regarding moving of the printing medium at a distance which is larger than (m+a)xc3x97L (a is positive integer) and is shorter than (m+a+1)xc3x97L, the distance being measured as a distance between respective ejection openings located at a discharge side ends regarding the moving of the printing medium.
In a tenth aspect of the present invention, there is provided an ink jet printing apparatus for performing printing by using a printing head having a first ejection opening row including a plurality of ejection openings ejecting a first kind of ink and a second ejection opening row including a plurality of ejection openings ejecting a second kind of ink different from the first kind of ink and by ejecting ink to a printing medium from the printing head, the apparatus comprising:
control means for controlling the printing for an area, which has a length corresponding to a divided length of an ejection opening arranged length of at least one of the first and second ejection opening rows, to be completed by scanning the at least one of the first and second ejection opening rows to the area a plurality of times, between successive two times of scanning the printing medium is moved at a distance of the divided length, and assigning different ejection opening to the area from each of the plurality of times of scanning,
wherein printing of a first image is completed by using the first kind of ink ejected by the first ejection row, then printing of a second image adjacent to the first image completed is completed by using the second kind of ink ejected by the second ejection row, and the time of scanning in which printing is not performed on the area of the first image exists between the time of a last scanning for completing the first image and the time of a first scanning for printing the second image.
According to the above structure, when so-called multi-pass printing is performed, for the first and the second ejection opening rows, the positions of the ejection openings located at ends of the respective first and the second ejection opening rows on a paper feeding side or a paper discharging side in connection with feeding of a printing medium are apart from each other at a distance of (m+a)xc3x97L (a: positive integer) in a discharging or feeding direction for conveying a printing medium. Or between scanning for completing printing on a first image and first scanning for printing a second image, scanning with performing no printing is executed for an area on which the first image has been printed. Hence, printing an image by the first ejection opening row and printing an image, which is adjacent to the image by the first ejection opening row, by the second ejection opening row are performed while at least a single scanning is executed therebetween. Therefore, it is possible to provide time for fixing ink by the first ejection opening row onto the printing medium.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.